Food Flavours Flashcards
what are sensations produced by food in the mouth and nose?
taste: sweet, sour, salty, bitter, umami
odor: pungent, putrid, floral, ehtereal, minty, musty, camphoraceous
mouthfeel: pain, temp, tactile sensation
how are flavours perceived?
interactions between nasal cavity, receptors in mouth, teeth and jaws sends signals to the CNS for translation into what flavours are perceived
what is found in food that elicites sweet taste?
electronegtive elements in molecules
common elements are O and N:
- O: alcohols (glycerols and glucose), aldehydes, cinnamaldehyde
- N: peptides and amino acids
what is used as a reference for sweetness of sugars?
glucose
assigned number 1
what sugars are the same sizes but different levels of sweetness?
lactose and sucrose
glucose and fructose
what are the two groups of amino acids? what are these groups based on?
D and L amino acids
based on their optical activities (one rotates clockwise and the other rotates anticlockwise)
this results in differences due to interactions in the mouth receptors
are D or L amino acids sweeter?
D is always sweeter than L
how is sucrose broken down?
invertase breaks down glucose and fructose bond
results in a mixture of glucose and fructose, which is sweeter than the solution of sucrose (known as invert sugars)
what monosaccharides compose sucrose?
glucose and fructose
what are invert sugars?
broken down components of sucrose (glucose and fructose)
glucose and fructose (the invert sugars) are sweeter than the original sugar
what does amylase break down in corn syrup?
glucose hydrolysate
what is high fructose corn syrup broken down into?
what enzyme does this?
glucose isomerase breaks down fructose into hydrolysate, comprised of glucose and fructose
what are traditional sweeteners?
sucrose (regular sugar) invert sugars corn syrup high fructose corn syrup (HFCS) maltodextrose
what are examples of food used traditionally as sweeteners?
honey
maple
molasses
what compounds are found in honey?
fructose (33-40%)
glucose (32-40%
water (15-20%)
significant phenolic content
what sugars are found in maple?
glucose
fructose
sucrose
what are molasses?
dark syrup liquid left after recovery of sugar from either sugar cane or sugar beet
describe how molasses are made
- crush sugar cane to create juice. Heat juice to concentrate. Separate sugar crystals and syrup (molasses)
- continue to heat syrup. Separate into crystals and syrup (cane molasses)
- continue to heat. Separate into crystals and another syrup (black syrup molasses)
how does the color and viscosity change as you keep heating molasses syrup?
they increase
what is found in sugar cane?
vit B6 iron Mg K manganese calcium
high intensity synthetic sweeteners are ____ and ____ than traditional sweeteners
cheaper: easy production
less caloric: synthetic sweeteners are not as readily metabolized
what is the result of synthetic sweeteners not being as readily metabolized?
less calories
mouth bacteria don’t break them down to acids, which cause decay
what are factors that affect sweetener use?
- cost
- calories
- sweeter equivalence with
- sugar (isosweetness)
- solubility and viscosity (must be H2O soluble and dissolve at the same rate)
order the polyols according to relative sweetness
- xylitol (isosweet with sucrose)
- malitol
- manitol
- sorbitol
- isomalt
- polyextros
what sweetener is isosweet as sucrose?
xylitol
what is synergy
mixing multiple sugars and sweeteners (who have different viscosity and sweetness) together in solution
what are polyols?
polyhydric alcohols
what are common food products that use synergy? what is their ratio used?
chewing gum: 3:2 xylitol to sorbitol
sugar free products: 4:1 ratio of maltitol and xylitol
which is the sweetest polyol?
xylitol
isosweet to sucrose
does polyol have an aftertaste?
no
why is xylitol useful for diabetes?
metabolized independently of insulin
why is xylitol resistant to fermentation of oral bacteria?
they don’t cause pH decline (as with sucrose) to demineralize tooth enamel and cause decay
why is xylitol considered low calorie?
it is not metabolized in the gut
main properties of xylitol?
- sweetest polyol (isosweet to sugar)
- has no discernible aftertaste
- metabolized independently of insulin
- resitant to fermentation by oral bacteria
- bacteriocidal
- stable to heat (good for baked goods)
- doesn’t react with AA (no browning occurs)
why does xylitol not cause browning in foods?
it does not react with amino groups or compounds, thus it does not lead to non-enzymatic browning reactions
what are examples of products manufactured with xylitol?
candies gums diabetic food oral hygiene products pharmaceutirals
what is the effect of polyol consumption?
since they are not readily metabolizked, too much intake can lead to enhanced bowel movement
what are types of high intensity sweeteners?
- natural
2. synthetic
compare D and L synthetic high intensity sweeteners
D: insipid (tasteless)
L: sweeter
compare D and L natural high intensity sweeteners
D: sweeter than L (like usual)
L: insipide (tasteless) or bitter
what are 4 examples of natural sweeteners
glycine
d-tryptophan
miraculin
ketemfe
what is special about glycine?
does not have a chiral carbon
thus, no D or L forms
how much sweeter is D-tryptophan than sucrose?
30 to 40 times sweeter
what is beta-chloro-6-tryptophan
derivative of D-tryptophan
1500x sweeter than sucrose
what is miraculin
berry in west africa
if eaten by itself, it is bland. If you eat anything else after (even bitter or sour foods), it will taste sweet
gives an effect of taste modifiation
what is a food that creates taste modification?
miraculin
what is ketemfe
a fruit that produces a peptide rich hydrolysate which is several time sweeter that sucrose
the hydrolysate is known as thaumatin
what is thaumatin
the hydrolysate produced in ketemfe, which is several times sweeter than sucrose
what is stevia
shrub found in sub-tropical and tropical zones in south america
several times sweeter than sucrose
what is the active compound in stevia?
glycosides of steviol (an alcohol)
what are 3 examples of synthetic sweeteners?
aspartame
acesulfame potassium
sucralose (aka splenda)
what are 3 examples of synthetic sweeteners?
aspartame
acesulfame potassium
sucralose (aka splenda)
saccharin
what is aspartame commercially known as?
equal
nutrasweet
what products is aspartame commonly found in?
gums
yogurts
beverages
how much sweeter is aspartame compared to sucrose?
200 times
why is aspartame not suitable for cooked or baked products?
why is it harmful when exposed to heat?
it is heat labile
high heat can cause aspartame to break down into components (methanol is harmful)
what is the defective enzyme in PKU? What is PKU?
PKU is phenylketonuria
defective enzyme is phenylalanine hydrolase
This results in phenylalanine not being utilized, thus it will accumulate and cause mental disorders
which sweetener must be used in combination with other sweeteners?
acesulfame potassium
can acesulfame potassium be used in heat?
yes because it is heat stable
how is acesulfame potassium found in markets?
in the form of tablets
what is saccharine?
Na salt + Cl salt
what is saccharine? why was it not permitted for human consumption until recently?
a synthetic sweetener
it was shown to cause tumors in bladders of rats
can saccharin be used in cooked and baked products?
yes, it is heat stable
what is the brand name for sucraloase?
splenda
what form is sucralose (aka splenda) found in supermarkets?
sachets or granulated forms
describe the chemical structure of sucralose in comparison to sucralose
it is the trichloro derivative of sucrose
heat stable
out of all synthetic sweeteners, which ones are heat stable and which are not?
heat stable: acesulfame-K, saccharin and sucralose
no: aspartame
how much sweeter is sucralose than sucrose?
6000x sweeter
why is sucralose not “caloric”?
it is not metabolized in the gut and does not supply calories as sugar
what chemical components creates a salty taste? what reactions are they formed in?
- salt ions (Na+, K+, Cl-)
- formed in neutralization reactions
- salty taste is dependent on the size of ions (smaller ions are salty, larger ions are bitter)
smaller salt ions are ____ and larger ions are _____
salty
bitter
CsCl, KI, MgSO are ____ ions
bitter
PbAC and BeAc are ____ ions
sweet
LiCl, LiBr, NaNO, KCl are ____ ions
salty
what are functions and uses of NaCL?
- imparts salty taste
- preserves food
- flavor enhancer
- source of electrolytes
- enhances production of stomach acid (stimulates and aids digestion)
how does salt act to preserve food?
salt decreases water activity = microbial activity will decrease = enzymatic activity decreases because enzymes are covered in a layer of salt
how much NaCl can people tolerate? what happens when food has higher than this percent?
2%
beyond this, NaCl may render the product indigestible or nauseating
what are health issues related with NaCl consumption?
hypertension
high blood pressure
what are ways to reduce NaCl levels in food?
- addition of spices
- salt substitues
- replacing Na compounds with compounds of other cations (eg. KHCO3 instead of NaHCO3)
what are types of salt substitutes?
mineral based subs: salt of ions other than Na+ (eg, K+ and NH4+) to stimulate NaCl in taste
vegetized salt substitutes: powdered dehydrated vegetables as a base
what are examples of commercial salt substitutes?
NH4Cl KCl citric acid citrates starch glutamic acid glutamates
what are the 3 classes or organic compounds responsible for bitternesS?
alkaloids
glycosides
peptides (with hydrophobic and aromatic characteristics)
what are alkaloids
- one class of organic compounds responsible for bitterness
- nitrogenous
- widely distributed in plants
what are examples of alkaloids?
quinine
caffeine
theobromine
what is quinine
- an alkaloid (exhibits bitter tastes)
- white amorphous powder
- limited solubility in H2O
- one of the most bitter substances known
- used in beverages
describe the solubility of quinine
limited solubility in H2O
what is one of the most bitter substances known?
quinine
what is caffeine?
- crystalline purine derivates found in coffee beans, tea leaves and cola nuts
- solubility in H2O is 1:50 at room temp or 1:2 at 65degc
- stimulant wit GRAS status
what is theobromine? what is it structually related to? where is it found?
- related to caffeine
- found with caffeine in various flants (eg. cocoa beans and cola nuts)
what are glycosides?
- creates bitter tastes
- aglycones esterified with various sugars
what are examples of glycosides?
narigin
hesperidin
coniferin
sinigrin
what is narigin
what is it found in?
- a glycoside (causes bitter tastes)
- found in grapefruit and bitter orange
- one of the most bitter substances known
what does the hydrolysis of narigin yield?
d-rhamnoglucose and glycone
what is hesperidin? what is it found in?
- a glycoside (causes bitter tastes)
- found in sweet orange and citrus fruits
what does the hydrolysis of hesperidin yield?
yields rutinose and aglycone hesperetin
what is coniferin? where is it found?
- a glycoside (causes bitter tastes)
- found in conifer wood
what does the hydrolysis of coniferin yield?
coniferyl alcohol, which can be further oxidized to vanillin
what compound is vanillin oxidized from?
coniferyl alcohol, which is a product of the hydrolysis of coniferin
what is sinigrin?
black mustard seeds
what does the hydrolysis of sinigrin yield?
glucose and allyl isothiocyanate
which compound makes taste buds insensitive to sweet and bitter?
gymnemic acid
what is the miracle fruit?
how does this compound work?
makes bitter and sour compounds taste sweet, eve though it was tasteless by itself
it inhibits the bitter or sour taste to sweet molecules
what are two criteria to taste sensitivity of sweet molecules??
solubility: the sweet molecules must be in saliva to interact with the sweet receptors. Thus, it must be able to be soluble in saliva
concentration: need to have a threshold value to be perceived as sweet
compare the taste and smell threshold level of the taste sensitivity of sweet molecules
taste has a higher threshold value
what can salt in a food enhance?
acid in a food (eg. adding salt to grapefruit)
sweet taste
what are the 3 components of mouthfeel?
pain
temperature
tactile sensations
describe how food will influence mouthfeel via pain
what compounds do this?
when compounds in foods interact with pain receptors in mouth and mucous membrane to cause irritation and pain
compounds: zingerone, gingerol, shagol, ally isothiocyanate
describe how food will influence mouthfeel via hot temperature
volatile compounds will leave product and interact more effectively with taste receptors
molecules move vigorously and interact again more effectively
describe how food will influence mouthfeel via cold temperature
molecules interact less effectively
can cause numbness
what are tactile sensations? what does it allow for?
allows feeling of texture, astringency and consistency
what are flavor enhancers?
what are examples?
compounds that improve or intensify flavour quality in foods
eg. MSG and maltol
how does maltol act as a flavour enhancer?
where/how is it formed?
- maltol is one of the products formed in the caramelization of sugar
- produces the “nutty” taste”
- used in enhancing flavour in baked goods
sub-threshold levels of salt reduces ____ in foods
sourness
sub-threshold levels of acids reduces ____ in foods
saltiness
sub-threshold levels of sugar reduces ____ in foods
saltiness
what methods are used with taste panelling in sensory evaluation?
preference and difference testing
describe preference panel taste testing
what is it most useful in?
choosing foods we prefer over others
most useful in food product development where large segments of population is used to verify product acceptability
what are the 3 kinds of preference taste testing
- simple paired comparison test
2 hedonic scale - ranking test
describe the simple paired comparison test
a pair of samples is provided to panel and are asked to select the one they prefer in terms of a particular attribute
describe the hedonic scale (type of preference taste panel)
a point system used to verify degree of likeness or dis-likeness of a product. (like extremely, like very much, like moderately, like slightly, neutral, dislike slightly, dislike moderately, etc…)
describe the ranking test (type of preference taste panel)
panel is provided with more than 2 samples and asked to rank them in order of preferences
what is difference testing?
verifying differences in particular attributes (eg firmness, juiciness, etc…) in a food product
what are the 6 kinds of difference testing?
1. simple paired comparison test 2 scheffe's paired comparison test 3. multiple paired comparison test 4. triangle test 5. duo-trio test 6. ranking test
describe the scheffe’s paired comparison test
similar to the simple paired comparison test, except that panel is asked to indicate or quantify degree of difference
describe the multiple paired comparison test
3 or more samples are compared against one another (A,B,C,D)
A with B
A with C
A with D
etc…
describe the triangle test
panel is presented with 3 samples and told that 2 of them are identical and required to pick the odd one
describe the duo trio test
similar to triangle test. Panel is presented with 3 samples and one is given as a reference. Eg. A, B, C. If C is given as the reference, the panelist must choose which two are the same and which is the odd one
compare the duo-trio and the triangle test. which is better?
Triangle test is better because the probability of choosing the right one is lower than in duo-trio test
what are the seven primary odors?
- Ethereal: thin rod-shaped molecules
- Camphoraceous: hemispherical-shaped molecules
- Musky: flat disk shaped;10A in diameter
- Floral: shaped as keyholes
- Minty: wedge-shaped molecules
- Pungent: negatively charged molecules
- Putrid: positively charged molecules
what ions cause sour taste/tartness?
H+ ions from acids (eg. lactate, pyruvate, acetate…)
what determines the degree of sourness?
what is it not determined by?
H+ concentration
not determined by total acidity of food
how might a food affect the perception of sourness?
components in a food might interact with the H+ ions, and change the perception of sourness
what are other factors that affect sour taste, besides H+ ion concentration?
nature of acidic group
buffering capacity
presence of other compounds
what are 3 ways that acid is important in food?
- preservation
- imparts flavor
- stabilizes products
what are 2 ways that acid is used for preservation?
- lowers pH: creates an environment that is less condusive to growth of microorgansms and restrict enzymatic activity
- enhances natural antioxidants by acting as metal ion chelators
how does acid affect vitamin C?
acid causes vitamin C to behave like an antioxidant in its reduced state (ketoascorbic acid)
what is the reduced state of vit C?
ketoascorbic acid
what is an example of acidity imparting flavor in foods?
wine
what are inorganic acids used in foods?
H3PO4 (phosphoric acid)
HCl (hydrochloric acid)
the majority of acids used in foods are….
what are examples?
organic acids:
- acetic
- citric
- fumaric
- lactic
- tartaric
- malic
- benzoic
- scorbic
describe acetic acid
what flavor does it give in foods?
- sharp and piquant. Clear and colorless
- gives aromitc flavor
how is acetic acid commercially prepared?
- by oxidation of CH3CHO (acetaldehyde) or butane
2. yeast fermentation of fruit juices, sucrose, glucose, malt…
what is the most abundant organic acid in fruits and veg?
citric acid
what are the characteristics of citric acid?
- white crystalline powder
- no smell
- very soluble in H2O and alcohol
- can be used to replace vinegar because it has no odor
what can be used to replace acetic acid?
citric acid
because it has no odor
what are characteristics of lactic acid?
- pale, yellow, viscous liquid
- pungent smell
what products is lactic acid used in?
milk and dairy
what are characteristics of fumaric acid?
- odorless, white granular or crystalline powder
- sparingly soluble in H2O
- soluble in ethanol
how is fumaric acid produced?
produced during fermentation of glucose of molasses by Rhizopus species
what is fumaric acid most used in?
food products where solubility is not a significant quality
what is scorbic and benzoic acid used mostly fod?
food preservation
scorbic and benzoic acid can be in what forms?
- free form
2. salt form (K, Na, Ca salts)
